Centrifugal fan

ABSTRACT

A centrifugal fan is described. The centrifugal fan is suitable for a portable electrical apparatus. A tongue shape is formed from a volute sidewall of a casing of the centrifugal fan. The volute sidewall is formed with at least one groove substantially extending horizontally at the tongue shape. Therefore, when the blades rotate to generate a wake flow to blow on a surface of the volute sidewall at the tongue shape, noise generated by the centrifugal fan can be reduced.

RELATED APPLICATIONS

The present application is based on, and claims priority from, Taiwanapplication Ser. No. 93133855, filed Nov. 5, 2004, the disclosure ofwhich is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a centrifugal fan, and moreparticularly, to a centrifugal fan with a surface of a volute sidewallat a tongue shape being formed with at least one groove substantiallyextending horizontally.

2. Description of the Related Art

A heat dissipation module is necessary to provide effective heatdissipation for a portable electrical apparatus, and especially for anotebook personal computer (PC), so as to allow the best performance.When heat accumulates in and cannot dissipate from the apparatus, theelectrical devices and the apparatus as a whole cannot work normally.The computer system, in particular, will crash. However, in order tosatisfy the market requirement for mobilization, sufficient space cannotbe possibly formed in the casing of the notebook PC for naturalconvection. Because heat dissipation design for high-frequency deviceshas encountered its bottleneck, the heat dissipation module of thenotebook PC tends to dissipate heat with forced convection generated bya centrifugal fan.

Reference is made to FIGS. 1 and 1A, which depict a perspective view anda top plan view showing a centrifugal fan of the prior art. Thecentrifugal fan 10, installed in a portable electrical apparatus such asa notebook PC, comprises a casing 11 and blades 31. The casing 11 has avolute sidewall 13 and a bottom plate 15, and the casing 11 defines acavity 17 and an outlet 19. A volute channel 21 is jointly defined bythe cavity 17 and the outlet 19, and a tongue shape 23 is formed fromthe volute sidewall 13 on a side of the outlet 19. The blades 31 aredisposed vertically with a rotational axis 33 on the bottom plate 15 inthe cavity 17. Rotation of blades 31 drives a horizontal airflow 25. Thehorizontal airflow 25 can be exhausted via dynamic and static pressuresgenerated by the horizontal airflow 25 passing through the volutechannel 21.

The outlet 19 of the prior art uses a curved surface and divergent ductwith a constant cross-section, which means a surface 16 of the volutesidewall 13 at the tongue shape 23 is parallel to the rotational axis33. This makes the airflow generate dynamic and static pressure, whichresists outside force to achieve the effect of heat dissipation.

Reference is made to FIG. 2, which depicts a schematic diagram showing awake flow generated by the centrifugal fan of the prior art blowing onthe volute sidewall at the tongue shape. When the wake flow 35 generatedby the blades 31 is blowing on the surface 16 of the volute sidewall 13at the tongue shape 23, each blasting point 41 is generated and regardedas a sound source that generates narrow band noise 43. Because thesurface 16 of the volute sidewall 13 at the tongue shape 23 is parallelto the rotational axis 33, according to the superposition principle, thenarrow band noise 43 with a large amplitude 45 and constant blade passfrequency will be generated. Once it is necessary to enhance theefficiency of the heat dissipation, the flow rate and the wind velocitymust be increased. However, the more the rotational speed and the flowrate are increased, the higher the frequency of the noise band is.Therefore, the noise is increasing. The trade off between the noise andthe heat dissipation is a serious problem.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a centrifugal fansuitable for a portable electrical apparatus. A tongue shape is formedfrom the volute sidewall of a casing of the centrifugal fan. The volutesidewall is formed with at least one groove substantially extendinghorizontally at the tongue shape. Therefore, when the blades rotate togenerate a wake flow to blow the surface of the volute sidewall at thetongue shape, noise generated by the centrifugal fan can be reduced.

According to the aforementioned aspect of the present invention, acentrifugal fan is provided, which is suitable for a portable electricalapparatus and comprises a casing having a bottom plate and a volutesidewall disposed on the bottom plate to define a cavity and an outlet.A tongue shape is formed from the volute sidewall on at least one sideof the outlet; and blades are disposed vertically with a rotational axison the bottom plate of the cavity. The volute sidewall is formed with atleast one groove substantially extending horizontally at the tongueshape.

In a preferred embodiment of the present invention, the aforementionedportable electrical apparatus is a notebook PC.

In a preferred embodiment of the present invention, a surface of theaforementioned volute sidewall at the tongue shape is, for example,formed with on or more grooves substantially extending horizontally.

The surface of the volute sidewall at the tongue shape of thecentrifugal fan of the invention is formed with at least one groovesubstantially extending horizontally, resulting in easy manufacture andimprovement of the issue of noise caused by the centrifugal fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1 and 1A depict a perspective view and a top plan view showing acentrifugal fan of the prior art;

FIG. 2 depicts a schematic diagram showing a wake flow generated by thecentrifugal fan of the prior art blowing on the volute sidewall at thetongue shape;

FIG. 3 depicts a perspective view showing a centrifugal fan inaccordance with a preferred embodiment of the present invention;

FIG. 4 depicts a schematic diagram showing a wake flow generated by thecentrifugal fan in accordance with a preferred embodiment of the presentinvention blowing on the volute sidewall at the tongue shape;

FIG. 4A illustrates the location of the groove with respect to theblades in accordance with a preferred embodiment of the presentinvention;

FIG. 5 depicts a cross-sectional view of a surface of a volute sidewallat a tongue shape in accordance with another preferred embodiment of thepresent invention;

FIG. 6 depicts a cross-sectional view of a surface of a volute sidewallat a tongue shape in accordance with another preferred embodiment of thepresent invention;

FIG. 7A illustrates the blade pass frequency of a centrifugal fan whereno groove is formed to the surface of the volute sidewall; and

FIG. 7B illustrates the blade pass frequency of a centrifugal fan whereone groove is formed to the surface of the volute sidewall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is made to FIG. 3, which depicts a perspective view showing acentrifugal fan in accordance with a preferred embodiment of the presentinvention. The centrifugal fan 100 installed in a portable electricalapparatus such as a notebook PC, comprises a casing 111 and blades 131.The casing 111 has a volute sidewall 113 and a bottom plate 115, and thecasing 111 defines a cavity 117 and an outlet 119. A volute channel 121is jointly defined by the cavity 117 and the outlet 119, and a tongueshape 123 is formed from the volute sidewall 113 on a side of the outlet119. The blades 131 are disposed vertically with a rotational axis 133on the bottom plate 115 in the cavity 117, and preferably, the blades131 are disposed vertically to the bottom plate 115. Rotation of theblades 131 drives a horizontal airflow 125. The horizontal airflow 125can be exhausted via dynamic and static pressure generated by thehorizontal airflow 125 passing through the volute channel 121.Meanwhile, when horizontal airflow 125 is generated by the blades 131rotating, the blades 131 blow on a surface 116 of the volute sidewall113 at the tongue shape 123. A groove 118 is formed on the tongue shape123 and substantially extends horizontally to destruct the wavesuperposition resulted from a wake flow 135 (as shown in FIG. 4)generated by the blades 131 rotating on the surface 116 of the volutesidewall 113 at the tongue shape 123, so that the noise generated by thecentrifugal fan can be reduced. According to this invention, the groove118 may be integrally formed on the casing 111 by plastic injectionmolding, metal casting or metal stamping.

Reference is made to FIG. 4, which depicts a schematic diagram showing awake flow 135 generated by the centrifugal fan in accordance with apreferred embodiment of the present invention blowing on the volutesidewall at the tongue shape. When the wake flow 135 generated by theblades 131 is blowing on the surface 116 of the volute sidewall 113 atthe tongue shape 123 (as shown in FIG. 3), each blasting point 141 isgenerated and regarded as a sound source that generates narrow bandnoise 143. Because the surface 116 of the volute sidewall 113 at thetongue shape 123 is formed with a groove 118 substantially extendinghorizontally, the time at which each sound source is generated isdifferent. Therefore, comparing to priot amplitude 45 (as shown in FIG.2), the amplitude 145 can be substantially reduced as a result of lessconstructive interference of sound waves generated by the sound sourceson different time; that is to say, the narrow band noise 143 islessened.

According to this invention, a part of the groove 118 substantiallyextending horizontally on the surface 116 corresponds to where the wakeflow 135 of the blades 131 is blown. For example, reference is made toFIG. 4A, the groove 118 formed on the surface 116 of the volute sidewall 113 at the tongue shape 123 is located to face the blades 131 at amidpoint of a height direction of the blades 131. The groove 118alternatively be located to face an upper side or a lower side withrespect to the height direction of the blades 131, so long as a part ofthe groove 118 corresponds to where the wake flow 135 of the blades 131are blown. In addition, the surface 116 of the volute sidewall 113 atthe tongue shape 123 may also be formed with two ore more grooves 118substantially extending horizontally. FIG. 4A depicts a perspective viewshowing a centrifugal fan in accordance with a preferred embodiment ofthe present invention, where the groove 118 substantially extendinghorizontally on the surface 116 is of a rectangular cross-section.

FIG. 5 depicts a cross-sectional view of a surface of a volute sidewallat a tongue shape in accordance with another preferred embodiment of thepresent invention, wherein the surface 116 is formed thereon with twogrooves 118 each of rectangular cross-section. FIG. 6 depicts across-sectional view of a surface of a volute sidewall at a tongue shapein accordance with another preferred embodiment of the presentinvention, wherein the surface 116 is formed with a groove 118 a of arounded cross-section. However, this invention is not limited the abovenumber or cross-sectional shapes of the grooves. Persons having ordinaryskills in the relevant art should be able to comprehend this inventionand utilizes other means, in accordance with the actual needs, to adjustthe number or cross-sectional shapes of the grooves, or to combineplural grooves of different cross-sections on the surface, which are notdescribed in detail herein.

As mentioned above, the groove 118 formed on the surface of the volutesidewall 113 at the tongue shape 123 can effectively reduce theamplitude 145 of the noise. Hence, the broader band noise is obtained toallow a user to experience a better quality of sound.

FIG. 7A illustrates the blade pass frequency of a centrifugal fan whereno groove is formed to the surface of the volute sidewall. Significantblade pass frequency can be observed at the operation frequencies of 900Hz and 1900 Hz. FIG. 7B illustrates the blade pass frequency of acentrifugal fan where one groove is formed to the surface of the volutesidewall. FIG. 7B clearly illustrates the significant reduction of theblade pass frequency at the operation frequencies of 900 Hz and 1900 Hz.

Therefore, according to the aforementioned preferred embodiments, oneadvantage of the centrifugal fan of the present invention is that thesurface of the volute sidewall at the tongue shape of the centrifugalfan is formed with at least one groove substantially extendinghorizontally. Therefore, when the blades rotate to generate a wake flowto blow on the surface of the volute sidewall at the tongue shape, noisegenerated by the centrifugal fan can be reduced.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrated of the presentinvention rather than limiting of the present invention. It is intendedthat various modifications and similar arrangements be included withinthe spirit and scope of the appended claims, the scope of which shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar structure.

1. A centrifugal fan, suitable for a portable electrical apparatus,comprising: a casing, the casing having a volute sidewall to define acavity and an outlet, wherein a tongue shape is formed from the volutesidewall on at least one side of the outlet; blades disposed around andvertically with a rotational axis on the casing; and at least one grooveset on the volute sidewall, the groove substantially extendinghorizontally at the tongue shape.
 2. The centrifugal fan according toclaim 1, wherein the portable electrical apparatus is a notebookpersonal computer (PC).
 3. The centrifugal fan according to claim 1,wherein the groove has a rectangular cross-section.
 4. The centrifugalfan according to claim 1, wherein the groove has a rounded cross-section5. The centrifugal fan according to claim 1, wherein the groove is suchlocated that a part of the groove faces the blades along a heightdirection of the blades.
 6. The centrifugal fan according to claim 5,wherein the groove is such located that the groove faces the blades at amidpoint of the height direction of the blades.
 7. A casing ofcentrifugal fan, suitable for a portable electrical apparatus,comprising: a bottom plate; a volute sidewall to define a cavity and anoutlet, wherein a tongue shape is formed from the volute sidewall on atleast one side of the outlet; and at least one groove formed on thetongue shape of the volute sidewall, the groove substantially extendinghorizontally at the tongue shape.
 8. The casing of centrifugal fanaccording to claim 7, wherein the portable electrical apparatus is anotebook PC.
 9. The casing of centrifugal fan according to claim 7,wherein the groove has a rectangular cross-section.
 10. The casing ofcentrifugal fan according to claim 7, wherein the groove has a roundedcross-section.
 11. The casing of centrifugal fan according to claim 7,wherein the bottom plate rotatably supports blades thereon, and whereinthe groove is such located that a part of the groove faces the bladesalong a height direction of the blades after the blades are supported onthe bottom plate.
 12. The casing of centrifugal fan according to claim11, wherein the groove is such located that the groove faces the bladesat a midpoint of the height direction of the blades.